57Fe-Mossbauer spectroscopy

Keywords Fe-exchanged zeolite A, 57Fe Mossbauer spectroscopy, hydrothermal crystallization... 

The samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, 57Fe Mossbauer spectroscopy [2] and Rutherford backscattering spectrometry (RBS). 

Properties of FeCr,o solid samples have been studied by X-ray diffraction, 57Fe Mossbauer spectroscopy and magnetic measurements to stimulate the interaction of Fe with fullerene. FeCr,o samples have been prepared by decomposition of the 1,3-dipolar cycloadduct of the fullerene and ferrocene nitrile oxide. The components exhibit super paramagnetic properties originating from an interaction between FeCr,o complexes within the nano-particles. Each nano-particle consists of hundreds to thousands complexes (546). 

The recoilless nuclear resonance absorption of y-radiation (Mossbauer effect) has been verified for more than 40 elements, but only some 15 of them are suitable for practical applications [33, 34]. The limiting factors are the lifetime and the energy of the nuclear excited state involved in the Mossbauer transition. The lifetime determines the spectral line width, which should not exceed the hyperfine interaction energies to be observed. The transition energy of the y-quanta determines the recoil energy and thus the resonance effect [34]. 57Fe is by far the most suited and thus the most widely studied Mossbauer-active nuclide, and 57Fe Mossbauer spectroscopy has become a standard technique for the characterisation of SCO compounds of iron. 

Fe HB(C2H2N3)3 2] has been obtained by dehydration under heating of the low-spin hexahydrate. The crystal structure for this hexahydrate has been determined at room temperature [17]. It clearly contains Fe(II) ions in the low-spin state (average Fe-N distance=1.99 A). The dehydrated derivative [Fe HB(C2H2N3)3 2] has been reported to exhibit a very abrupt spin transition between 334-345 K via variable temperature UV-vis and 57Fe Mossbauer spectroscopy studies [19]. After the publication of a preliminary magnetic study in 1994 [19], a more detailed report appeared in 1998 [20]. 

Fig. 19 LIESST effect observed by 57Fe Mossbauer spectroscopy for [Fe(btzp)3](Cl04)2 at 5 K, without light irradiation (top) at 5 K, after light irradiation (middle) at 125 K, after light irradiation (bottom). (Reprinted with permission from [87]. Copyright (2000) American Chemical Society)... 

Most interestingly, [Fe(btzp)3](Cl04)2 is the first one-dimensional Fe(II) spin crossover compound, which shows the LIESST effect, detected in this instance by 57Fe Mossbauer spectroscopy (Fig. 19). 

De Grave, E., Eeckhout S.G., McCammon, C.A. (1999a) Selected applications of 57Fe Mossbauer spectroscopy to mineral studies. Hyp. Interact. 122 21-38... 

Further identification of the particles is made with 57Fe Mossbauer spectroscopy. Mossbauer spectra were recorded with a conventional constant acceleration spectrometer with 57Co in Rh matrix as a y-ray source. Velocity calibration was made using a 5-pm a-Fe foil at 293 K. Figure 1.6.10 shows the Mossbauer spectra of the sample recorded at 293 K and 4.2 K. Spectra were fitted with theoretical... 

Miinck, E. Aspects of 57Fe Mossbauer spectroscopy. In Physical Methods in Bioinorganic Chemistry Spectroscopy and Magnetism, Lawrence Que, J., Jr., Ed. University Science Books Sausalito, CA, 2000 pp 287-319. 

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